Geographical awareness of user-carried devices combined with short-range wireless networking induces a fundamental shift in distributed system paradigms: contrary to the Internet model that abstracts away location, systems of mobile users are tightly coupled with the real geographic world.

This new characteristic of distributed systems is not taken into account in traditional computing models and toolboxes.

To provide a complete solution to deal with systems of interconnected mobile devices, we are working in two complementary directions: the definition of suitable computing models, and the definition and implementation of algorithmic building blocks for resilience in such systems.

We are working on providing formal reasoning framework based on realistic and usable models that include user mobility, failures and connectivity. The interest of these mobility-explicit computing models is twofold: first, they serve as a basis to provide formal proofs of resilience algorithms, and second, they provide inputs for dependability evaluation in mobile systems.

The computational counterpart to such models is the provision of a toolbox to ease the programming of systems with explicit mobility. We are focusing on the definition of algorithmic building blocks such as storage, agreement and membership. These building blocks may be classified with respect to their primary goal: they either take advantage of mobility, e.g., by providing localized services [Roy et al. 2008], as shown in Figure 1, or aim to hide the intrinsic complexity of mobility from the programmer, by providing a classical distributed systems interface.

Figure1: An example of a localized shared storage service

[Roy et al.-2008] Matthieu Roy, François Bonnet, Leonardo Querzoni, Silvia Bonomi, Marc-Olivier Killijian, David Powell. Geo-registers: an Abstraction for Spatial-based Distributed Computing. 12th International Conference On Principles Of DIstributed Systems (OPODIS’08). December 15th-18th 2008